Neuro-cognitive deficits observed in chronic alcoholics often mirror those observed in individuals with HIV-1 associated dementia (HAD). Given the patterns of similarity including neuropathological changes (neuronal dropout and decreased dendrite density) in HAD patients and alcohol abusers, it has been suggested that alcohol may serve as an accomplice in development on HAD and exacerbate the symptoms. Indeed, it has been shown that CNS suffers the additive effects of alcohol abuse and HIV infection. The mechanisms of such synergy remain elusive. It is generally agreed that the blood-brain barrier (BBB) is impaired in HAD and involves loss of tight junction (TJ) integrity. In addition, white matter abnormalities observed in chronic alcoholics are related to changes in BBB function. In this proposal, we attempt to evaluate the mechanism of alcohol-related modulation of HIV-1 encephalitis (HIVE). We hypothesize that alcohol abuse leads to direct alterations in monocyte migration during HIVE and that alcohol alters CNS immune responses through exacerbated BBB dysfunction. We will utilize our well-established model systems to study BBB changes in context of alcohol and HIV-1. We also propose exploratory studies to address specific cellular mechanisms underlying these phenomena. For this purpose, we will examine the myosin light chain kinase (MLCK) pathway of TJ disassembly in BBB and alterations in proteasomal function in endothelial cells and macrophages. To test these hypotheses, we will address three specific questions: 1) What are the effects of alcohol on monocyte migration across the BBB in HIVE? 2) Does BBB dysfunction due to TJ disassembly play a role in the impaired immune responses in HIVE? and 3) What are the possible mechanisms involved in alcohol-induced alterations in endothelial cell and macrophage function? We will employ a functional BBB model consisting of primary endothelial cells and astrocytes to study TJ disassembly, a xenograft animal model system for HIVE to evaluate in vivo immune responses and BBB dysfunction, and primary human cell models to decipher intracellular mechanisms. The ability to use an in vitro BBB and an in vivo animal model will help in defining mechanisms of disease progression in the setting of alcohol abuse.